Area Forecast Discussion
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FXUS61 KPBZ 261028
Area Forecast Discussion
National Weather Service Pittsburgh PA
628 AM EDT Mon Sep 26 2016
Showers and scattered thunderstorms can be expected with the
passage of cold front today. More seasonable temperatures are
expected for the rest of the week.
.NEAR TERM /THROUGH TONIGHT/...
Deepening trough over the Great Lakes will push a cold front,
currently analyzed over eastern Indiana, across the Upper Ohio
valley this afternoon. Model consensus on timing is relatively
good between the deterministic models and the hi res short term
guidance. As such, very little adjustment was needed to
categorical probabilities with strengthening support for
thunderstorms as the boundary approaches southwestern PA/northern
WV. This will be where surface instability is likely to be the
highest based on the boundary`s timing, and less cloud cover.
The NAM is the most robust with it`s CAPE/dewpoints compared to
other model guidance, including the RAP and HRRR soundings, which
it tends to overdue in most convective scenarios. However, with
deep layer shear present and at least modest cape of 500j/kg,
some strong to severe storms may be possible which is supported
by the spc marginal risk over the aforementioned region.
Strong southerly flow and sunshine in advance of the boundary
should allow for temperatures to warm above seasonal averages this
afternoon followed by normal low temperatures with the fronts
passage progged to be east of the ridges by midnight.
.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
Temperature advection will be rather weak on Tuesday with
southwesterly flow expected aloft with the upper trough still
situated over the northern Great Lakes and high pressure present
at the surface. Thus, temperatures were forecast just below
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Most of this period will be dominated by the closed upper
low...which will dive from Michigan into the central Ohio Valley by
Thursday and linger as a cutoff through at least Friday. Models are
beginning to converge on this scenario, with the lagging GFS finally
coming around. As such, mostly chance PoPs were maintained through
the remainder of the work week for scattered showers. Timing of
shortwaves around the upper low remains tricky at this distance.
Given the upper low representing a pattern change, felt the
SuperBlend temperatures were a bit too high and knocked them back a
couple of degrees early on, keeping daytime values a bit below
The upper low should begin to lift out by next weekend as midlevel
heights build over the lower Ohio Valley. This will bring dry
weather back by Sunday, as well as allow temperatures to recover
back to seasonal levels.
.AVIATION /12Z MONDAY THROUGH FRIDAY/...
VFR conditions are expected at the start of the TAF period with
only some high clouds. MVFR clouds hugging the ridges to our east
may still build into DUJ over the next hour or two, and then mix
out after sunrise.
A cold front, preceded by a warm front, will cross during the
afternoon and early evening hours. A short period of MVFR or even
IFR visibilities in showers or thunderstorms is expected, but the
exact timing of restrictions is still up in the air. Continued to
use a period of VCTS at most locations for now. Some of the
storms may be strong, with heavy rain and gusty winds. General
wind gusts of 15 to 20 knots are possible during the afternoon as
Scattered showers and MVFR ceilings may linger for a few hours
behind the front, until drier air sweeps in and allows skies to
clear overnight. Expect enough mixing to preclude much fog after
.OUTLOOK /MONDAY NIGHT THROUGH THURSDAY/...
The next chance for restriction is expected by Wednesday as upper
level low pressure settles into the area.